Plan for the weather to be cooler than you expect at the start (especially the marathon). You're starting right around dawn and you're at altitude. It'll be cold. Use the gloves and mylar blanket they give you and perhaps bring some throwaway clothes or something your can put in your gear bag just before the start.
And as for pace... this is a a unique race in that if you typically run a set pace, expect to run a faster race than normal. Rather than going by time, go by effort. Stick with your normal effort and you'll naturally go faster. But don't take off like a bat out of hell at the start. Even though it's downhill, you're still running a half (or full marathon).